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Extending Informix®Beyond standard relational database objects, HCL Informix® can be extended to handle specialized data types, access methods, routines, and other objects. Informix® includes many built-in extensions that are fully integrated in the database server. Informix® also provides DataBlade® modules, which are packages of extended database objects for a particular purpose and that are installed separately from the database server. Alternatively, you can create your own user-defined objects for Informix®.
Creating extensionsYou can create user-defined data types, routines, access methods, and other database objects to suit your needs. You can use application programming interfaces to write user-defined routines and applications that access data in Informix® databases.
DataBlade® API Programmer's GuideThe Informix® DataBlade® API Programmer's Guide describes information about the DataBlade® API, the C-language application programming interface (API) provided with HCL Informix®.
Database access
Execute user-defined routinesThis section provides information about how to call a user-defined routine (UDR).
Access MI_FPARAM routine-state informationWhen the routine manager calls a UDR, it passes the routine-state information as an extra argument, called the function-parameter structure, to the routine. This function-parameter structure, MI_FPARAM, holds the routine-state information for the C UDR with which it is associated.
Saving a user stateThe routine manager provides information about arguments and return values of a UDR in the MI_FPARAM structure that is associated with a UDR. In addition, you can store the address of private-state information, called user-state information, in a special field of the MI_FPARAM structure.
Saving user-state information in the first invocation of a UDR

Saving user-state information in the first invocation of a UDR

About this task

To save user-state information in the first invocation of a UDR:

Procedure

Use the mi_fp_funcstate() function to retrieve the user-state pointer from the MI_FPARAM structure.
After the UDR has the user-state pointer, it can obtain state information from the private storage area on subsequent invocations.
Check for a NULL-valued user-state pointer.
On the first invocation of your UDR, the user-state pointer is a NULL-valued pointer. If the user-state pointer is a NULL-valued pointer, allocate a private user-defined buffer or structure for the user-state information.
When you allocate memory for the user-state information, you must protect this memory so that it is not reclaimed while it is still in use. Define a memory duration of PER_COMMAND for this memory with a DataBlade® API memory-allocation function such as mi_dalloc() or mi_switch_mem_duration().
Put the private data in the user-defined buffer or structure to initialize the user state.
If the UDR has just allocated the private user-state buffer, use the mi_fp_setfuncstate() function to store the address of this user-defined buffer or structure as a user-state pointer in the MI_FPARAM structure.
You save the user-state pointer in the MI_FPARAM structure so that later UDR invocations of the routine sequence can access the routine-state information.

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